1. Field
One or more embodiments of the present invention relate to a photoacoustic probe and a photoacoustic diagnostic apparatus including the same that are used in diagnosis from photoacoustic images.
2. Description of the Related Art
A photoacoustic imaging technology uses a photoacoustic effect to noninvasively image biological tissues. When a biological tissue is irradiated with a short electromagnetic laser pulse for photoacoustic imaging, some of the optical energy from the laser pulse is absorbed by the biological tissue and subsequently converted into heat, thereby causing transient thermo-elastic expansion. The thermo-elastic expansion leads to emission of wideband ultrasound waves, and the emitted ultrasound waves are detected by ultrasound transducers from different directions and reconstructed into images.
Since photoacoustic imaging is based on the conversion of optical energy into ultrasound waves for detection, this method has advantages of combining properties of optical imaging with those of ultrasound imaging. Pure optical imaging has much higher contrast ratio than ultrasound imaging, but permits only limited imaging up to a predetermined depth from a surface of a living tissue due to strong optical scattering inside soft tissues. On the other hand, ultrasound imaging provides a sufficiently high spatial resolution so as to examine a fetus. Photoacoustic imaging overcomes the drawback of optical imaging such as low imaging depths with conversion of optical energy into ultrasound waves due to a photoacoustic effect, thereby achieving both a high optical contrast ratio and a high spatial resolution.
Photoacoustic imaging techniques have already been developed significantly to conduct research on tumors, brains, hearts, and eyeballs of small animals. A photoacoustic imaging system may easily be integrated with a conventional ultrasound imaging system after undergoing only a slight modification such as removal of an ultrasound transmission function.
However, a photoacoustic diagnostic apparatus uses a laser for generating a short electromagnetic pulse whose absorption may cause a thermo-elastic expansion, and such a laser has significantly high optical energy.